1. Technical Field
The present invention relates to liquid ejecting heads such as ink jet recording heads that eject liquid droplets from a nozzle using pressure fluctuations, and to liquid ejecting apparatuses provided with such liquid ejecting heads.
2. Related Art
Ink jet recording heads (called simply “recording heads” hereinafter) used in image recording apparatuses such as ink jet recording apparatuses (called simply “printers” hereinafter), coloring material ejecting heads used in the manufacture of color filters such as liquid-crystal displays, electrode material ejecting heads used in the formation of electrodes in organic EL (electroluminescence) displays and FEDs (field emission displays), bioorganic matter ejecting heads used in the manufacture of biochips (biochemical devices), and so on can be given as examples of liquid ejecting heads that eject a liquid within a pressure chamber as liquid droplets from a nozzle by causing a pressure fluctuation to occur.
The aforementioned recording head includes: a flow channel unit in which a serial liquid flow channel spanning from a reservoir to nozzles via respective pressure chambers is formed, where ink in liquid form is introduced from a liquid holding unit such as an ink cartridge that has been filled with ink; an actuator unit having a pressure generation element capable of causing a fluctuation in the volume of a pressure chamber; and so on. With a recording head in which multiple nozzles are arranged in a row and pressure chambers communicating with the nozzles are arranged along the nozzle row direction, the configuration is such that multiple ink supply openings that communicate with the pressure chambers are formed in the inner wall surface of the reservoir, which holds the ink to be introduced to the pressure chambers, on the side of the reservoir on which the pressure chambers are arranged; meanwhile, liquid introduction openings are provided in locations that face the center, in the lengthwise direction, of the inner wall surface on the opposite side, and ink introduced therefrom into the reservoir is supplied to the pressure chambers via the ink supply openings.
With recording heads configured with multiple pressure chambers arranged in this manner, an increase in the number of pressure chambers that are arranged causes the distance from the liquid introduction opening to increase the further the pressure chamber is toward the end in the arrangement direction, which leads to the risk that an insufficient amount of ink will be supplied. Meanwhile, although increasing the volume of the reservoir, increasing the diameter of the liquid introduction openings, or the like can be considered as a way to equalize the amount of ink supplied to the respective pressure chambers, doing so causes a problem in that the size of the recording head in the width direction thereof will increase. Accordingly, forming partition plates (branch portions) that cut across the liquid introduction openings that open into the reservoir in those liquid introduction openings has been proposed as a configuration that enables ink introduced from the liquid introduction openings to be stably supplied to the end of the pressure chamber arrangement direction in the reservoir without leading to an increase in the size of the recording head in the width direction (JP-A-11-286110).
However, with a recording head having a partition plate as described above, when two or more liquid introduction openings are formed in the reservoir, the flow of the ink stagnates in the area of an interflow region, where the inks introduced from the respective liquid introduction openings flow together, that is on the side opposite to the pressure chamber, and there has been a tendency for foam contained in the ink to build up in this stagnant area.
In addition, in the case where reservoirs are provided in parallel, even if an attempt is made to reduce the dimensions of the reservoirs in the width direction, it is necessary to form the liquid introduction openings as openings that protrude in order to stably supply the ink introduced from the liquid introduction openings to the end of the pressure chamber arrangement direction in the reservoirs, and it has not been possible to reduce the distance between adjacent parallel reservoirs in order to prevent the protruding cavities from interfering with each other. Furthermore, even if the wall surfaces that face the protruding cavities of the parallel reservoirs are sunk into the reservoirs in correspondence thereto, the flow channel width of the sunk areas will become narrower than the flow channel widths in other areas, and there has thus been a tendency for foam to build up in a stagnant area occurring around this sunk area, and in particular in the bottom of the sunk area. For this reason, when applying a pressure fluctuation to the pressure chambers and ejecting ink, the foam that has built up is sometimes introduced into the pressure chambers, thus causing ejection problems such as so-called “missing dots”, in which ink is not ejected properly from the nozzles.